The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been d...The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been discussed.Here we give a proof-of-concept illustration on the intrinsic facets effect by employing the popularly investigated NH2-MIL-125(Ti)MOFs with{001},{111}and{100}facets controllably exposed as model photocatalysts,which were synthesized via a simple supersaturation strategy free of any capping agents.Compared to conventional synthetic routes with capping agents employed,the NH2-MIL-125(Ti)MOFs obtained in this work exhibit remarkably different physical and chemical properties such as surface wettability,charge separation as well as trend of facets effect on photocatalytic water splitting performance.The main reason has been unraveled to originate from unavoidable residue/influence of capping agents during the conventional facets-controlled synthetic routes leading to changed local surface structural environment as well as distinct charge separation property.Our results demonstrate the importance and feasibility of facets-controllable synthesis free of capping agents in getting insight into the intrinsic facets effect of MOFs-related materials.展开更多
Laboratory experiments were conducted to determine the effects of total dissolved gas （TDG） supersaturation on acute lethality and avoidance responses in juvenile rock carp （Procypris rabaudi Tchang）. The juvenile...Laboratory experiments were conducted to determine the effects of total dissolved gas （TDG） supersaturation on acute lethality and avoidance responses in juvenile rock carp （Procypris rabaudi Tchang）. The juvenile rock carp were exposed to water with different levels of supersaturation （105%, 115%, 120%, 125%, 130%, 135%, 140%, and 145%） and depth of 0.20 m at 25℃ for 60 h. Median lethal time （LT50） was used to assess the lethal responses corresponding to different levels of gas supersaturation. The results show that half of the juvenile rock carp died at the 120%, 125%, 130%, 135%, 140%, and 145% levels of supersaturation, and the LT50 corresponding to different levels of supersaturation was 18.7, 15.4, 8.2, 6.6, 3.5, and 1.7 h. When the level of supersaturated water is below 115%, the mortality is negligible. Avoidance responses were observed 5 min after the fish were put into equilibrated water （99%, 0.08 m deep） and water with different supersaturated levels （105%, 115%, 125%, 135%, and 145%, 0.08 m deep） at 25 ℃. The fish exhibited strong avoidance responses in supersaturated water when the gas supersaturation was above 135%. However, they exhibited an obvious preference to supersaturated water when the gas supersaturation was below 115%. Thus, the juvenile rock carp can likely survive in water with a supersaturated level of 115%.展开更多
To investigate the effect of supersaturation induced by micelle formation during dissolution on the bioavailability of itraconazole(ITZ)/Soluplus~? solid dispersion. Solid dispersions prepared by hot melt extrusion (H...To investigate the effect of supersaturation induced by micelle formation during dissolution on the bioavailability of itraconazole(ITZ)/Soluplus~? solid dispersion. Solid dispersions prepared by hot melt extrusion (HME) were compressed into tablets directly with other excipients. Dissolution behavior of ITZ tablets was studied by dissolution testing and the morphology of micelles in dissolution media was studied using transmission electron microscopy (TEM). Drug transferring from stomach into intestine was simulated to obtain a supersaturated drug solution. Bioavailability studies were performed on the ITZ tablets and Sporanox~? in beagle dogs. The morphology of micelles in the dissolution media was observed to be spherical in shape, with an average size smaller than 100 nm. The supersaturated solutions formed by Soluplus~? micelles were stable and no precipitation took place over a period of 180 min. Compared with Sporanox~?, ITZ tablets exhibited a 2.50-fold increase in the AUC (0–96) of ITZ and a 1.95-fold increase in its active metabolite hydroxyitraconazole (OHITZ) in the plasma of beagle dogs. The results obtained provided clear evidence that not only the increase in the dissolution rate in the stomach, but also the supersaturation produced by micelles in the small intestine may be of great assistance in the successful development of poorly water-soluble drugs. The micelles formed by Soluplus~? enwrapped the molecular ITZ inside the core which promoted the amount of free drug in the intestinal cavity and carried ITZ through the aqueous boundary layer(ABL), resulting in high absorption by passive transportation across biological membranes. The uptake of intact micelles through pinocytosis together with the inhibition of P-glycoprotein-mediated drug efflux in intestinal epithelia contributed to the absorption of ITZ in the gastrointestinal tract. These results indicate that HME with Soluplus~?, which can induce supersaturation by micelleformation, may be of great assistance to the successful development of poorly watersoluble drugs.展开更多
Batch crystallization in acidic aqueous solution of cephalexin was conducted by reactive crystallization with or without seeding. Supersaturation was generated by mixing ammonia and acidic aqueous solution of cephalex...Batch crystallization in acidic aqueous solution of cephalexin was conducted by reactive crystallization with or without seeding. Supersaturation was generated by mixing ammonia and acidic aqueous solution of cephalexin and controlled by solution feeding rate and seeding conditions. UV and Morphologi G3 were used to measure supersaturation and aspect ratio. Experimental results demonstrated that burst nucleation occurred and the products were needle-like at high supersaturation;meanwhile, the products were plate-like and had high aspect ratio at low supersaturation. Analysis of the measured supersaturation profi les and corresponding aspect ratio explained the mechanisms governing the aspect ratio. The optimized operating parameters were also proposed (seeding supersaturation is equal to 1.3, seed mass ratio 8% and feeding rate 368 μL/min).展开更多
In order to realize accurate dynamic control of supersaturation and to study condensation growth characteristics of nanoparticles through different levels of super saturation,a series of parametric analyses and system...In order to realize accurate dynamic control of supersaturation and to study condensation growth characteristics of nanoparticles through different levels of super saturation,a series of parametric analyses and systematic comparisons between two-stage and three-stage operating temperature designs were simulated with COMSOL Multiphysics.The simulation results showed that the three-stage operating temperature did not change peak supersaturation compared with two operating temperatures,and the three-stage operating temperature was superior in decreasing the amount of water vapor and the temperature,thus lowering particle loss and variation in detection and collection.The peak supersaturation level increased by 0.3 as the flow rate increased from 0.6 to 2.0 L/min,but the supersaturation peak moved from 0.0027 z0 to 0.08 z0(i.e.,the growth time and the final size decreased by 40%).Peak supersaturation increased as the temperature difference increased or the temperature difference window was shifting left,and minimum activation size decreased.Shifting the 70℃temperature difference window from 9℃,79℃-1℃,71℃for the condenser and initiator temperatures resulted in peak supersaturation in the centerline being above 5.8,and the activation size changed as low as 1 nm.Experiments with flow rates varying by a factor of 2.5(from 0.6 to 1.5 L/min)resulted in a final size decrease of 43%(from 3.2 to 1.8μm),and experimental results of outlet particle size distributions were equivalent with theoretical analysis as the operating temperature was changed.展开更多
Nanocrystals(NCs),a colloidal dispersion system formulated with stabilizers,have attracted widespread interest due to their ability to effectively improve the oral bioavailability of poorly water-soluble drugs.The sta...Nanocrystals(NCs),a colloidal dispersion system formulated with stabilizers,have attracted widespread interest due to their ability to effectively improve the oral bioavailability of poorly water-soluble drugs.The stabilizer plays a key role because it can affect the physical stability and even the oral bioavailability of NCs.However,how stabilizers affect the bioavailability of NCs remains unknown.In this study,F68,F127,HPMC,and PVP were each used as a stabilizer to formulate naringenin NCs.The NCs formulated with PVP exhibited excellent release behaviors,cellular uptake,permeability,oral bioavailability,and anti-inflammatory effects.The underlying mechanism is that PVP effectively inhibits the formation of naringenin dimer,which in turn improves the physical stability of the supersaturated solution generated when NC is dissolved.This finding provides insights into the effects of stabilizers on the in vivo performances of NCs and supplies valuable knowledge for the development of poorly water-soluble drugs.展开更多
More and more high dams have been constructed and operated in China. The total dissolved gas （TDG） supersaturation caused by dam discharge leads to gas bubble disease or even death of fish, Through a series of exper...More and more high dams have been constructed and operated in China. The total dissolved gas （TDG） supersaturation caused by dam discharge leads to gas bubble disease or even death of fish, Through a series of experiments, the conditions and requirements of supersaturated TDG generation were examined in this study. The results show that pressure （water depth）, aeration, and bubble dissolution time are required for supersaturated TDG generation, and the air-water contact area and turbulence intensity are the main factors that affect the generation rate of supersaturated TDG. The TDG supersaturation levels can be reduced by discharging water to shallow shoals downstream of the dam or using negative pressure pipelines. Furthermore, the TDG supersaturation levels in stilling basins have no direct relationship with those in reservoirs. These results are of great importance for further research on the prediction of supersaturated TDG generation caused by dam discharge and aquatic protection.展开更多
Ice nuclei-supersaturation spectra in the form of a Power Law ( Ni=RSir; B and y are empirical constants) have been expressed since 1973 when the curve was first introduced independentally by Gagin and Huffman. Experi...Ice nuclei-supersaturation spectra in the form of a Power Law ( Ni=RSir; B and y are empirical constants) have been expressed since 1973 when the curve was first introduced independentally by Gagin and Huffman. Experiments performed with a thermal gradient diffusion chamber in order to investigate the validity of the power curve. The results show that a linear curve fit to the data is as good as the power curve. The linear curve has the coefficients of correlation between 0.75 and 0.93 whereas the power curve fit to the same data has the coefficients between 0.82 and 0.93. The data reported by other workers, Zamurs and Jiusto and Zamurs et al., exhibit the same trend.展开更多
AIM To demonstrate that urinary supersaturation per se is not a reliable diagnostic measure of the risk for stone formation.METHODS Available physical and chemical data for calcium oxalate monohydrate(COM) and calcium...AIM To demonstrate that urinary supersaturation per se is not a reliable diagnostic measure of the risk for stone formation.METHODS Available physical and chemical data for calcium oxalate monohydrate(COM) and calcium hydrogen phosphate dihydrate(brushite, BRU), and urinary supersaturations with respect to COM and BRU in healthy individuals and stone formers, were obtained from the literature. Classical theory of nucleation was used for calculations.RESULTS It was found that the rate of homogeneous nucleation(unaided by substrates) of COM and BRU is nil at all conceivable supersaturations of urine. Consequently spontaneous formation of crystals in urine requires the presence of nucleation substrates for(heteronuclei).CONCLUSION Urinary supersaturation with respect to lithiatic compounds is a necessary, but not a sufficient condition for nephrolithiasis. The absence of crystallization inhibitors and the presence of efficient nucleation promoters(heteronuclei) in urine are further necessary conditions of urolithiasis occurrence. Urinary supersaturation per se is not a reliable diagnostic measure of the risk of kidney stone formation.展开更多
High-quality silver nanowires(Ag NWs)are essential for the next-generation flexible transparent conductors(TCs).However,current synthesis methods predominantly rely on inefficient empirical trial-and-error approaches,...High-quality silver nanowires(Ag NWs)are essential for the next-generation flexible transparent conductors(TCs).However,current synthesis methods predominantly rely on inefficient empirical trial-and-error approaches,lacking a universal theoretical framework.Here,we employ the results of thermodynamic analysis to precisely control the in-situ formation of ideal Ag nuclei with tailored crystalline phases and exposed surfaces via supersaturation modulation,enabling the efficient synthesis of high-quality Ag NWs.We found that the addition of two-dimensional additives,such as graphitic carbon nitride(g-C_(3)N_(4)),MoS_(2),WS_(2),Ti_(3)C_(2)T_(x),and graphene oxide(GO),effectively reduces the supersaturation of the crystal growth units,thereby suppressing random nucleation and favoring the formation of high-purity penta-twinned seeds with low-surface-energy(111)facets.Such control over nuclei allows the production of Ag NWs with an average length of 227μm(aspect ratio>2200)at a yield of 93%.Consequently,the resulting TCs exhibit a transmittance(T)of 87%at 550 nm and a sheet resistance(R_(sq))of 5Ω/sq,outperforming conventional indium tin oxide(ITO)(typically,T=84%at 550 nm,R_(sq)=10Ω/sq).Furthermore,when used as transparent heaters,they can reach approximately 118℃ with a rapid heating rate of 10.5℃/s at a low voltage of just 5 V.This study innovatively proposes a universal mechanism for synthesizing high-quality Ag NWs,facilitating their diverse applications.展开更多
One of the possible negative environmental effects of hydropower stations is the supersaturation of total dissolved gas (TDG) downstream of high-dams,which can lead to gas bubble disease or even death of fish. By taki...One of the possible negative environmental effects of hydropower stations is the supersaturation of total dissolved gas (TDG) downstream of high-dams,which can lead to gas bubble disease or even death of fish. By taking the TDG as the main study object,the paper launched the TDG field observations on Zipingpu,Three Gorges,Ertan,Manwan,Dachaoshan,Gongzui and Ertan dams in China. The factors affecting TDG generation and dissipation were explored. Energy dissipation structures,spill rates and operation patterns were the main factors causing TDG supersaturation. TDG saturations are essentially the same in the hydro-electric tail water and in the upper reaches,so hydro-electric tail water can be less TDG supersaturated through mixing downstream. The main factors affecting the dissipation process of the supersaturated TDG were tributary convergence,water depth and turbulence. TDG supersaturation was unevenly distributed in both the vertical and transverse directions. This study is important because it adds to the accumulating experience of TDG field observations of dam projects in China,and because it objectively and impartially evaluates the impacts of supersaturated TDG. The study also provides field data and references for future studies of TDG supersaturation caused by high-dams.展开更多
Controlling the nucleation and growth of organic-inorganic hybrids perovskite is of key importance to improve the morphology and crystallinity of perovskite films. However, the growth mechanism of perovskite films bas...Controlling the nucleation and growth of organic-inorganic hybrids perovskite is of key importance to improve the morphology and crystallinity of perovskite films. However, the growth mechanism of perovskite films based on classical crystallization theory is not fully understood. Here, we develop a supersaturation controlled strategy(SCS) to balance the nucleation and crystal growth speeds. By this strategy, we are able to find an ideal supersaturation region to realize a balance of nucleation and crystal growth, which yields highly crystallized perovskite films with micrometer-scale grains. Besides, we provide a thoughtful analysis of nucleation and growth based on the fabrication of the perovskite films. As a result, the highest photovoltaic power conversion efficiencies(PCE) of 19.70% and 20.31% are obtained for the planar and the meso-superstructured devices, respectively. This strategy sheds some light for understanding the film growth mechanism of high quality perovskite film, and it provides a facile strategy to fabricate high efficiency perovskite solar cells.展开更多
Swift cooling crystallization of vanillin was investigated in water,ethanol,isopropanol and ethyl acetate.Morphology and polymorph evolution of vanillin were discussed in terms of solvent,supersaturation ratio and sil...Swift cooling crystallization of vanillin was investigated in water,ethanol,isopropanol and ethyl acetate.Morphology and polymorph evolution of vanillin were discussed in terms of solvent,supersaturation ratio and silica template.PXRD,DSC,FTIR and microscope were used to identify polymorphs of vanillin.Results showed that the nucleated polymorphs of vanillin depended largely on the solvent,supersaturation ratio and silica template.Low supersaturation ratios favor the nucleation of stable form I in water,and high supersaturation ratio exceeds 7 generating 100%metastable form II.However,if the supersaturation ratio is too high(S>8),liquid-liquid phase separation will occur,and no crystals could be obtained.In other solvents such as ethanol,isopropanol and ethyl acetate,only form I was obtained.However,it should be noted that the morphology of form I prepared in ethanol,isopropanol and ethyl acetate is distinct from that obtained in water,the former is flake-like and the latter is rod-like.The nucleation of vanillin from different solution was also studied with the presence of SiO_(2),SiO_(2)-NH_(2)and SiO_(2)−COOH templates,which did not change the nucleated polymorph of vanillin,but changed the nucleation and growth rate of stable form I.展开更多
Drug particles with spherical morphology possess amazing advantages in terms of particle flowability,mechanical properties,drug solubility,and bioavailability.The growth mechanism of drug spherulite is of great import...Drug particles with spherical morphology possess amazing advantages in terms of particle flowability,mechanical properties,drug solubility,and bioavailability.The growth mechanism of drug spherulite is of great importance for the preparation and regulation of spherulites.Herein,ceftriaxone sodium spherulites were fabricated by the antisolvent crystallization method using dropwise addition of ceftriaxone sodium solution to acetone.Online observation of the whole crystallization process combined with electron microscopy technique revealed the spherical growth process from amorphous form to spherulites.As the supersaturation of the crystallization system was adjusted,the ceftriaxone sodium crystals transformed from amorphous form to spherulites.In the process of antisolvent crystallization with acetone as antisolvent,when the theoretical supersaturation degree S was higher than 2.62,the crystallization system tended to appear amorphous form;when S was between 2.57 and 2.62,the amorphous form transformed into clustered spherulites;when S was less than 2.57,the surface of spherulites will be covered with flaky crystal,which transformed into urchin-like type.With the understanding of the spherical growth mechanism,the ceftriaxone sodium spherulites prepared in this research with modified supersaturation control had a low residue of antisolvent acetone,and the flowability was significantly improved.展开更多
Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle...Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle size and settling performance remain unclear.In this study,the growth behavior of CuS particles generated by two sulfide precipitation methods,gas-liquid and liquid-liquid sulfidation,was investigated.The effects of acidity,sulfur-to-copper molar ratio,and temperature on particle size were analyzed.The results showed that increasing the temperature had an adverse effect on CuS particle growth.Additionally,we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system.Based on supersaturation calculations and XPS analysis,it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation,while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge.This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.展开更多
Ag-Cu alloys are extensively used in sliding electric contacts due to their superior electrical conductivity,but their limited wear resistance reduces component longevity.Surface severe plastic deformation(SSPD)has em...Ag-Cu alloys are extensively used in sliding electric contacts due to their superior electrical conductivity,but their limited wear resistance reduces component longevity.Surface severe plastic deformation(SSPD)has emerged as a promising method to enhance wear resistance and reduce friction of metals without altering the matrix composition.In this study,an Ag-20 wt.%Cu alloy was subjected to SSPD for various durations,with the aim of improving tribological performance.The microstructure,hardness,and current-carrying tribological performance under different currents were systematically investigated,along with an exploration of the underlying mechanisms.The results show that in addition to introducing a high density of dislocations on the surface,SSPD also encourages the formation of(111)texture,and particularly disperses the initially long strips of Curich phase into short strips and fine particles.It promotes a tribo-film composed primarily of a mixture of Cu_(2)O and CuO that forms on the worn surface of the surface-treated sample under the 1 A current,thus significantly reducing the friction coefficient and electrical noise.Under the 10 A current,the sample treated for 60 min possesses the optimal friction coefficient(0.429),wear rate(0.791×10^(−6)mm^(3)/(N m)),and electrical noise(0.240 V).In contrast to the Ag/Cu layered structure observed on the worn subsurface of the untreated sample,a single-phase Ag(Cu)solid solution forms on the worn subsurface of the 60-min treated sample,which improves the current-carrying tribological performance.This work provides valuable insights for the development and application of electrical contact alloys with excellent performance.展开更多
Sintered metals serving as thermal interface materials(TIMs)with superior thermal conductivities show the most promise in meeting the heat dissipation requirements of next-generation wide bandgap applications.Neverthe...Sintered metals serving as thermal interface materials(TIMs)with superior thermal conductivities show the most promise in meeting the heat dissipation requirements of next-generation wide bandgap applications.Nevertheless,their thermal stabilities during high-temperature service provide significant challenges.Herein,a facile approach was developed for one-step synthesis of single-phase Ag-Cu supersaturated solid-solution nanoparticle(Ag-Cu SS-NP)pastes with adjustable Cu contents(up to 37.7 at.%),and they exhibited ultrahigh resistance to oxidation and excellent sinterability.A paste composed of Ag-Cu SS-NPs was sintered in air at 250℃ for 20 min,and this resulted in a dense supersaturated structure with an impressive thermal conductivity of 157.8 W/(m K)and a room-temperature shear strength of 133.4 MPa.Microstructural analyses demonstrated that Cu had precipitated from the Ag lattice to form Cu nanoprecipitates,which refined the grain sizes and induced high-density dislocations during sintering.For the pinning effect of dislocations and grain boundaries by the Cu nanoprecipitates and coherent twins,the high-temperature(400℃)shear strength of sintered Ag-Cu SS-NP joints was significantly improved by 67%(58.6 MPa),meanwhile the shear strength after long-term aging at 200 and 300℃for 960 h were increased by 123%(140.3 MPa)and 80%(82.4 MPa)compared to those of sintered Ag NP joints,respectively.The remarkable thermal stability is far superior to traditional TIMs,so the Ag-Cu SS-NP paste exhibits excellent potential as a TIM for high-temperature power device applications.展开更多
Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials ...Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, NH3 and H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst＇s metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate.展开更多
The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving ...The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulation results including the distribution of the local supersaturation ratio distribution in the precipitator, mean crystal size and coefficient of variation under different operating conditions compared well with experimental data in the literature. The effect of the presence of a draft tube on precipitation were also investigated, and it is suggested that the installation of a draft tube increased the mean crystal size, in general agreement with experimental work in the literature.展开更多
Total dissolved gas supersaturation(TDGS) appears when the pressures of gases in a solution exceed the barometric pressures.TDGS is often caused by flood discharge at dams.It may lead to gas bubble disease(GBD) for fi...Total dissolved gas supersaturation(TDGS) appears when the pressures of gases in a solution exceed the barometric pressures.TDGS is often caused by flood discharge at dams.It may lead to gas bubble disease(GBD) for fish and biochemical responses of selected fish and other aquatic organisms.The purpose of this study was to determine the impact of long-term TDGS levels on the growth and biochemical responses of rock carp(Procypris rabaudi Tchang) dwelling in the upper reaches of the Yangtze River.Three-year-old rock carp were exposed to TDGS levels at 100%,104%,108%,112%,and 116% for 42 d.Samples were taken every 7 d after the start of the trial in order to determine catalase(CAT) and superoxide dismutase(SOD) activities in gill and muscle tissues.Samples were taken at Days 0 and 42 of exposure to determine growth rate.Little effect was found on growth rate in all treatment groups.SOD and CAT activities varied in different tissues,according to time of exposure and TDGS levels.The biochemical response of fish exposed to TDGS was more obvious in gill tissue than in muscle tissue.Surveys of SOD and CAT activities in different tissues offer important information about the effect of TDGS on the rare fish in the Yangtze River,and may help evaluate the risk to the aquatic eco-environment and aquatic ecosystem in the downstream of the Yangtze River.展开更多
文摘The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been discussed.Here we give a proof-of-concept illustration on the intrinsic facets effect by employing the popularly investigated NH2-MIL-125(Ti)MOFs with{001},{111}and{100}facets controllably exposed as model photocatalysts,which were synthesized via a simple supersaturation strategy free of any capping agents.Compared to conventional synthetic routes with capping agents employed,the NH2-MIL-125(Ti)MOFs obtained in this work exhibit remarkably different physical and chemical properties such as surface wettability,charge separation as well as trend of facets effect on photocatalytic water splitting performance.The main reason has been unraveled to originate from unavoidable residue/influence of capping agents during the conventional facets-controlled synthetic routes leading to changed local surface structural environment as well as distinct charge separation property.Our results demonstrate the importance and feasibility of facets-controllable synthesis free of capping agents in getting insight into the intrinsic facets effect of MOFs-related materials.
基金Project (No. 50979063) supported by the National Natural Science Foundation of China
文摘Laboratory experiments were conducted to determine the effects of total dissolved gas （TDG） supersaturation on acute lethality and avoidance responses in juvenile rock carp （Procypris rabaudi Tchang）. The juvenile rock carp were exposed to water with different levels of supersaturation （105%, 115%, 120%, 125%, 130%, 135%, 140%, and 145%） and depth of 0.20 m at 25℃ for 60 h. Median lethal time （LT50） was used to assess the lethal responses corresponding to different levels of gas supersaturation. The results show that half of the juvenile rock carp died at the 120%, 125%, 130%, 135%, 140%, and 145% levels of supersaturation, and the LT50 corresponding to different levels of supersaturation was 18.7, 15.4, 8.2, 6.6, 3.5, and 1.7 h. When the level of supersaturated water is below 115%, the mortality is negligible. Avoidance responses were observed 5 min after the fish were put into equilibrated water （99%, 0.08 m deep） and water with different supersaturated levels （105%, 115%, 125%, 135%, and 145%, 0.08 m deep） at 25 ℃. The fish exhibited strong avoidance responses in supersaturated water when the gas supersaturation was above 135%. However, they exhibited an obvious preference to supersaturated water when the gas supersaturation was below 115%. Thus, the juvenile rock carp can likely survive in water with a supersaturated level of 115%.
基金the National Natural Science Foundation of China(NSFC 81102399).
文摘To investigate the effect of supersaturation induced by micelle formation during dissolution on the bioavailability of itraconazole(ITZ)/Soluplus~? solid dispersion. Solid dispersions prepared by hot melt extrusion (HME) were compressed into tablets directly with other excipients. Dissolution behavior of ITZ tablets was studied by dissolution testing and the morphology of micelles in dissolution media was studied using transmission electron microscopy (TEM). Drug transferring from stomach into intestine was simulated to obtain a supersaturated drug solution. Bioavailability studies were performed on the ITZ tablets and Sporanox~? in beagle dogs. The morphology of micelles in the dissolution media was observed to be spherical in shape, with an average size smaller than 100 nm. The supersaturated solutions formed by Soluplus~? micelles were stable and no precipitation took place over a period of 180 min. Compared with Sporanox~?, ITZ tablets exhibited a 2.50-fold increase in the AUC (0–96) of ITZ and a 1.95-fold increase in its active metabolite hydroxyitraconazole (OHITZ) in the plasma of beagle dogs. The results obtained provided clear evidence that not only the increase in the dissolution rate in the stomach, but also the supersaturation produced by micelles in the small intestine may be of great assistance in the successful development of poorly water-soluble drugs. The micelles formed by Soluplus~? enwrapped the molecular ITZ inside the core which promoted the amount of free drug in the intestinal cavity and carried ITZ through the aqueous boundary layer(ABL), resulting in high absorption by passive transportation across biological membranes. The uptake of intact micelles through pinocytosis together with the inhibition of P-glycoprotein-mediated drug efflux in intestinal epithelia contributed to the absorption of ITZ in the gastrointestinal tract. These results indicate that HME with Soluplus~?, which can induce supersaturation by micelleformation, may be of great assistance to the successful development of poorly watersoluble drugs.
基金supported by the Major National Science and Technology Projects (No. 2017ZX07402003)Major National Scientifi c Instrument Development Project (No. 21527812)
文摘Batch crystallization in acidic aqueous solution of cephalexin was conducted by reactive crystallization with or without seeding. Supersaturation was generated by mixing ammonia and acidic aqueous solution of cephalexin and controlled by solution feeding rate and seeding conditions. UV and Morphologi G3 were used to measure supersaturation and aspect ratio. Experimental results demonstrated that burst nucleation occurred and the products were needle-like at high supersaturation;meanwhile, the products were plate-like and had high aspect ratio at low supersaturation. Analysis of the measured supersaturation profi les and corresponding aspect ratio explained the mechanisms governing the aspect ratio. The optimized operating parameters were also proposed (seeding supersaturation is equal to 1.3, seed mass ratio 8% and feeding rate 368 μL/min).
基金supported by Natural Science Foundation of China(No.91544218)the National Key Research and Development Program of China(No.2016YFC0201001)+2 种基金the Science and Technological Fund of Anhui Province for Outstanding Youth(1808085J19)the Science and Technological Fund of Anhui Province(1908085MD114)The CASHIPS Director’s Fund,Grant NO.YZJJ2019QN1
文摘In order to realize accurate dynamic control of supersaturation and to study condensation growth characteristics of nanoparticles through different levels of super saturation,a series of parametric analyses and systematic comparisons between two-stage and three-stage operating temperature designs were simulated with COMSOL Multiphysics.The simulation results showed that the three-stage operating temperature did not change peak supersaturation compared with two operating temperatures,and the three-stage operating temperature was superior in decreasing the amount of water vapor and the temperature,thus lowering particle loss and variation in detection and collection.The peak supersaturation level increased by 0.3 as the flow rate increased from 0.6 to 2.0 L/min,but the supersaturation peak moved from 0.0027 z0 to 0.08 z0(i.e.,the growth time and the final size decreased by 40%).Peak supersaturation increased as the temperature difference increased or the temperature difference window was shifting left,and minimum activation size decreased.Shifting the 70℃temperature difference window from 9℃,79℃-1℃,71℃for the condenser and initiator temperatures resulted in peak supersaturation in the centerline being above 5.8,and the activation size changed as low as 1 nm.Experiments with flow rates varying by a factor of 2.5(from 0.6 to 1.5 L/min)resulted in a final size decrease of 43%(from 3.2 to 1.8μm),and experimental results of outlet particle size distributions were equivalent with theoretical analysis as the operating temperature was changed.
基金by the National Natural Science Foundation of China(No.82173765)the Science Foundation for Outstanding Youth of Liaoning Province(2021-YQ-08)+5 种基金Ningxia Key Research and Invention Program(No.2021BEG02039)Basic Research Projects of Liaoning Provincial Department of Education(2020LFW01)the Career Development Program for Young Teachers in Shenyang Pharmaceutical University(ZQN2019003)the Outstanding Youth Lifting Program in Shenyang Pharmaceutical University(YQ202115)the Natural Science Foundation of Liaoning Province(2020-MS-074)Open Fund of Key Laboratory of Biotechnology and Bioresources Utilization(Dalian Minzu University),Ministry of Education(KF2022005),China.
文摘Nanocrystals(NCs),a colloidal dispersion system formulated with stabilizers,have attracted widespread interest due to their ability to effectively improve the oral bioavailability of poorly water-soluble drugs.The stabilizer plays a key role because it can affect the physical stability and even the oral bioavailability of NCs.However,how stabilizers affect the bioavailability of NCs remains unknown.In this study,F68,F127,HPMC,and PVP were each used as a stabilizer to formulate naringenin NCs.The NCs formulated with PVP exhibited excellent release behaviors,cellular uptake,permeability,oral bioavailability,and anti-inflammatory effects.The underlying mechanism is that PVP effectively inhibits the formation of naringenin dimer,which in turn improves the physical stability of the supersaturated solution generated when NC is dissolved.This finding provides insights into the effects of stabilizers on the in vivo performances of NCs and supplies valuable knowledge for the development of poorly water-soluble drugs.
基金supported by the National Natural Science Foundation of China (Grant No. 50979063)
文摘More and more high dams have been constructed and operated in China. The total dissolved gas （TDG） supersaturation caused by dam discharge leads to gas bubble disease or even death of fish, Through a series of experiments, the conditions and requirements of supersaturated TDG generation were examined in this study. The results show that pressure （water depth）, aeration, and bubble dissolution time are required for supersaturated TDG generation, and the air-water contact area and turbulence intensity are the main factors that affect the generation rate of supersaturated TDG. The TDG supersaturation levels can be reduced by discharging water to shallow shoals downstream of the dam or using negative pressure pipelines. Furthermore, the TDG supersaturation levels in stilling basins have no direct relationship with those in reservoirs. These results are of great importance for further research on the prediction of supersaturated TDG generation caused by dam discharge and aquatic protection.
文摘Ice nuclei-supersaturation spectra in the form of a Power Law ( Ni=RSir; B and y are empirical constants) have been expressed since 1973 when the curve was first introduced independentally by Gagin and Huffman. Experiments performed with a thermal gradient diffusion chamber in order to investigate the validity of the power curve. The results show that a linear curve fit to the data is as good as the power curve. The linear curve has the coefficients of correlation between 0.75 and 0.93 whereas the power curve fit to the same data has the coefficients between 0.82 and 0.93. The data reported by other workers, Zamurs and Jiusto and Zamurs et al., exhibit the same trend.
文摘AIM To demonstrate that urinary supersaturation per se is not a reliable diagnostic measure of the risk for stone formation.METHODS Available physical and chemical data for calcium oxalate monohydrate(COM) and calcium hydrogen phosphate dihydrate(brushite, BRU), and urinary supersaturations with respect to COM and BRU in healthy individuals and stone formers, were obtained from the literature. Classical theory of nucleation was used for calculations.RESULTS It was found that the rate of homogeneous nucleation(unaided by substrates) of COM and BRU is nil at all conceivable supersaturations of urine. Consequently spontaneous formation of crystals in urine requires the presence of nucleation substrates for(heteronuclei).CONCLUSION Urinary supersaturation with respect to lithiatic compounds is a necessary, but not a sufficient condition for nephrolithiasis. The absence of crystallization inhibitors and the presence of efficient nucleation promoters(heteronuclei) in urine are further necessary conditions of urolithiasis occurrence. Urinary supersaturation per se is not a reliable diagnostic measure of the risk of kidney stone formation.
基金support from the Natural Science Foundation of Changsha of Hunan Province,China(No.kq2402055)the National Natural Science Foundation of China(No.21872047).
文摘High-quality silver nanowires(Ag NWs)are essential for the next-generation flexible transparent conductors(TCs).However,current synthesis methods predominantly rely on inefficient empirical trial-and-error approaches,lacking a universal theoretical framework.Here,we employ the results of thermodynamic analysis to precisely control the in-situ formation of ideal Ag nuclei with tailored crystalline phases and exposed surfaces via supersaturation modulation,enabling the efficient synthesis of high-quality Ag NWs.We found that the addition of two-dimensional additives,such as graphitic carbon nitride(g-C_(3)N_(4)),MoS_(2),WS_(2),Ti_(3)C_(2)T_(x),and graphene oxide(GO),effectively reduces the supersaturation of the crystal growth units,thereby suppressing random nucleation and favoring the formation of high-purity penta-twinned seeds with low-surface-energy(111)facets.Such control over nuclei allows the production of Ag NWs with an average length of 227μm(aspect ratio>2200)at a yield of 93%.Consequently,the resulting TCs exhibit a transmittance(T)of 87%at 550 nm and a sheet resistance(R_(sq))of 5Ω/sq,outperforming conventional indium tin oxide(ITO)(typically,T=84%at 550 nm,R_(sq)=10Ω/sq).Furthermore,when used as transparent heaters,they can reach approximately 118℃ with a rapid heating rate of 10.5℃/s at a low voltage of just 5 V.This study innovatively proposes a universal mechanism for synthesizing high-quality Ag NWs,facilitating their diverse applications.
基金supported by the National Natural Science Foundation of China (Grant No.50979063)
文摘One of the possible negative environmental effects of hydropower stations is the supersaturation of total dissolved gas (TDG) downstream of high-dams,which can lead to gas bubble disease or even death of fish. By taking the TDG as the main study object,the paper launched the TDG field observations on Zipingpu,Three Gorges,Ertan,Manwan,Dachaoshan,Gongzui and Ertan dams in China. The factors affecting TDG generation and dissipation were explored. Energy dissipation structures,spill rates and operation patterns were the main factors causing TDG supersaturation. TDG saturations are essentially the same in the hydro-electric tail water and in the upper reaches,so hydro-electric tail water can be less TDG supersaturated through mixing downstream. The main factors affecting the dissipation process of the supersaturated TDG were tributary convergence,water depth and turbulence. TDG supersaturation was unevenly distributed in both the vertical and transverse directions. This study is important because it adds to the accumulating experience of TDG field observations of dam projects in China,and because it objectively and impartially evaluates the impacts of supersaturated TDG. The study also provides field data and references for future studies of TDG supersaturation caused by high-dams.
基金supported by the National Key Research and Development Program of China (2016YFA0204000)the National Natural Science Foundation of China (U1632118, 21571129)+2 种基金Shanghai Tech Start-Up Funding1000 Young Talent program,Science and Technology Commission of Shanghai Municipality (16JC1402100, 16520720700)
文摘Controlling the nucleation and growth of organic-inorganic hybrids perovskite is of key importance to improve the morphology and crystallinity of perovskite films. However, the growth mechanism of perovskite films based on classical crystallization theory is not fully understood. Here, we develop a supersaturation controlled strategy(SCS) to balance the nucleation and crystal growth speeds. By this strategy, we are able to find an ideal supersaturation region to realize a balance of nucleation and crystal growth, which yields highly crystallized perovskite films with micrometer-scale grains. Besides, we provide a thoughtful analysis of nucleation and growth based on the fabrication of the perovskite films. As a result, the highest photovoltaic power conversion efficiencies(PCE) of 19.70% and 20.31% are obtained for the planar and the meso-superstructured devices, respectively. This strategy sheds some light for understanding the film growth mechanism of high quality perovskite film, and it provides a facile strategy to fabricate high efficiency perovskite solar cells.
基金This work was financially supported by grants from the National Natural Science Foundation of China(grant Nos.22068002 and 22178054)Natural Science Foundation of Jiangxi Province(grant No.20202BABL203020)。
文摘Swift cooling crystallization of vanillin was investigated in water,ethanol,isopropanol and ethyl acetate.Morphology and polymorph evolution of vanillin were discussed in terms of solvent,supersaturation ratio and silica template.PXRD,DSC,FTIR and microscope were used to identify polymorphs of vanillin.Results showed that the nucleated polymorphs of vanillin depended largely on the solvent,supersaturation ratio and silica template.Low supersaturation ratios favor the nucleation of stable form I in water,and high supersaturation ratio exceeds 7 generating 100%metastable form II.However,if the supersaturation ratio is too high(S>8),liquid-liquid phase separation will occur,and no crystals could be obtained.In other solvents such as ethanol,isopropanol and ethyl acetate,only form I was obtained.However,it should be noted that the morphology of form I prepared in ethanol,isopropanol and ethyl acetate is distinct from that obtained in water,the former is flake-like and the latter is rod-like.The nucleation of vanillin from different solution was also studied with the presence of SiO_(2),SiO_(2)-NH_(2)and SiO_(2)−COOH templates,which did not change the nucleated polymorph of vanillin,but changed the nucleation and growth rate of stable form I.
基金the financial contribution from Central Guidance on Local Science and Technology Development Fund of Liaoning Province(grant No.2023JH6/100100004)National Key Research and Development Program of China(grant No.2021YFC2901300)+3 种基金National Natural Science Foundation of China(grant No.22021005,22378041)Fundamental Research Funds for the Central Universities(grant No.DUT22YG208,DUT22LAB603)Key Research and Development Projects in Shandong Province(grant No.2022CXGC010303)acknowledge the assistance of Dalian University of Technology Instrumental Analysis Center.
文摘Drug particles with spherical morphology possess amazing advantages in terms of particle flowability,mechanical properties,drug solubility,and bioavailability.The growth mechanism of drug spherulite is of great importance for the preparation and regulation of spherulites.Herein,ceftriaxone sodium spherulites were fabricated by the antisolvent crystallization method using dropwise addition of ceftriaxone sodium solution to acetone.Online observation of the whole crystallization process combined with electron microscopy technique revealed the spherical growth process from amorphous form to spherulites.As the supersaturation of the crystallization system was adjusted,the ceftriaxone sodium crystals transformed from amorphous form to spherulites.In the process of antisolvent crystallization with acetone as antisolvent,when the theoretical supersaturation degree S was higher than 2.62,the crystallization system tended to appear amorphous form;when S was between 2.57 and 2.62,the amorphous form transformed into clustered spherulites;when S was less than 2.57,the surface of spherulites will be covered with flaky crystal,which transformed into urchin-like type.With the understanding of the spherical growth mechanism,the ceftriaxone sodium spherulites prepared in this research with modified supersaturation control had a low residue of antisolvent acetone,and the flowability was significantly improved.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.52121004)the National Natural Science Foundation of China(No.52274414).
文摘Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle size and settling performance remain unclear.In this study,the growth behavior of CuS particles generated by two sulfide precipitation methods,gas-liquid and liquid-liquid sulfidation,was investigated.The effects of acidity,sulfur-to-copper molar ratio,and temperature on particle size were analyzed.The results showed that increasing the temperature had an adverse effect on CuS particle growth.Additionally,we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system.Based on supersaturation calculations and XPS analysis,it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation,while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge.This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.
文摘Ag-Cu alloys are extensively used in sliding electric contacts due to their superior electrical conductivity,but their limited wear resistance reduces component longevity.Surface severe plastic deformation(SSPD)has emerged as a promising method to enhance wear resistance and reduce friction of metals without altering the matrix composition.In this study,an Ag-20 wt.%Cu alloy was subjected to SSPD for various durations,with the aim of improving tribological performance.The microstructure,hardness,and current-carrying tribological performance under different currents were systematically investigated,along with an exploration of the underlying mechanisms.The results show that in addition to introducing a high density of dislocations on the surface,SSPD also encourages the formation of(111)texture,and particularly disperses the initially long strips of Curich phase into short strips and fine particles.It promotes a tribo-film composed primarily of a mixture of Cu_(2)O and CuO that forms on the worn surface of the surface-treated sample under the 1 A current,thus significantly reducing the friction coefficient and electrical noise.Under the 10 A current,the sample treated for 60 min possesses the optimal friction coefficient(0.429),wear rate(0.791×10^(−6)mm^(3)/(N m)),and electrical noise(0.240 V).In contrast to the Ag/Cu layered structure observed on the worn subsurface of the untreated sample,a single-phase Ag(Cu)solid solution forms on the worn subsurface of the 60-min treated sample,which improves the current-carrying tribological performance.This work provides valuable insights for the development and application of electrical contact alloys with excellent performance.
基金supported by the National Natural Science Foundation of China(Nos.52075125 and 52105331)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010591)the Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20210324124203009,JSGG20201102154600003,GXWD20231130103814001,and GXWD20220721182229001).
文摘Sintered metals serving as thermal interface materials(TIMs)with superior thermal conductivities show the most promise in meeting the heat dissipation requirements of next-generation wide bandgap applications.Nevertheless,their thermal stabilities during high-temperature service provide significant challenges.Herein,a facile approach was developed for one-step synthesis of single-phase Ag-Cu supersaturated solid-solution nanoparticle(Ag-Cu SS-NP)pastes with adjustable Cu contents(up to 37.7 at.%),and they exhibited ultrahigh resistance to oxidation and excellent sinterability.A paste composed of Ag-Cu SS-NPs was sintered in air at 250℃ for 20 min,and this resulted in a dense supersaturated structure with an impressive thermal conductivity of 157.8 W/(m K)and a room-temperature shear strength of 133.4 MPa.Microstructural analyses demonstrated that Cu had precipitated from the Ag lattice to form Cu nanoprecipitates,which refined the grain sizes and induced high-density dislocations during sintering.For the pinning effect of dislocations and grain boundaries by the Cu nanoprecipitates and coherent twins,the high-temperature(400℃)shear strength of sintered Ag-Cu SS-NP joints was significantly improved by 67%(58.6 MPa),meanwhile the shear strength after long-term aging at 200 and 300℃for 960 h were increased by 123%(140.3 MPa)and 80%(82.4 MPa)compared to those of sintered Ag NP joints,respectively.The remarkable thermal stability is far superior to traditional TIMs,so the Ag-Cu SS-NP paste exhibits excellent potential as a TIM for high-temperature power device applications.
文摘Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, NH3 and H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst＇s metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate.
基金Supported by the National Natural Science Foundation of China (Nos.20236050, 50134020) and the Special Funds for Major State Basic Research Program of China (973 Program, 2004CB217604).
文摘The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulation results including the distribution of the local supersaturation ratio distribution in the precipitator, mean crystal size and coefficient of variation under different operating conditions compared well with experimental data in the literature. The effect of the presence of a draft tube on precipitation were also investigated, and it is suggested that the installation of a draft tube increased the mean crystal size, in general agreement with experimental work in the literature.
基金Project (No. 50979063) supported by the National Natural Science Foundation of China
文摘Total dissolved gas supersaturation(TDGS) appears when the pressures of gases in a solution exceed the barometric pressures.TDGS is often caused by flood discharge at dams.It may lead to gas bubble disease(GBD) for fish and biochemical responses of selected fish and other aquatic organisms.The purpose of this study was to determine the impact of long-term TDGS levels on the growth and biochemical responses of rock carp(Procypris rabaudi Tchang) dwelling in the upper reaches of the Yangtze River.Three-year-old rock carp were exposed to TDGS levels at 100%,104%,108%,112%,and 116% for 42 d.Samples were taken every 7 d after the start of the trial in order to determine catalase(CAT) and superoxide dismutase(SOD) activities in gill and muscle tissues.Samples were taken at Days 0 and 42 of exposure to determine growth rate.Little effect was found on growth rate in all treatment groups.SOD and CAT activities varied in different tissues,according to time of exposure and TDGS levels.The biochemical response of fish exposed to TDGS was more obvious in gill tissue than in muscle tissue.Surveys of SOD and CAT activities in different tissues offer important information about the effect of TDGS on the rare fish in the Yangtze River,and may help evaluate the risk to the aquatic eco-environment and aquatic ecosystem in the downstream of the Yangtze River.
